Rockhounding in Washington a Quick Geologic History
Washington has some of the most important agate deposits in the United States, which include the famous Ellensburg Blue Agate.
Much of the richness of Washington's agates is a result of a long and often violent geological history filled with volcanic eruptions and huge sediment carrying glaciers.
The state of Washington can be has many geological regions and sub-regions thanks to the various flows, external rocks, and glaciers which have made their home throughout the state over the last 100 million years.
The western part of the state has been dominated by arc volcanism, in which the oceanic plate is submerged along with water rich rocks under the continental plate.
The water and more volatile rocks from the oceanic plate lower the melting point of the mantle, allowing the mantle to rise up and break through the continental crusts.
It is these actions which would seem to help make Washington State one of the best places to find agates in the country and which allows it to have such a rich verity of agates including the famous Ellensburg Blue Agate.
In some cases islands from distant regions are carried on the moving contents and will get scraped off and deposited in western Washington as the oceanic plate carrying them gets submerged.
This has create a number of rock locations called exotic terranes, rocks which are historically and geologically separate from the region in which they are found.
Moving East one finds what once the path of the Yellowstone hotspot, which created reddish-brown mineral deposits.
Such deposits are common in areas of lava flows rich in iron.
As lava rocks and ash are typically rich in silica's, and the viscous nature of these flows allows for many pockets within the rock, agates have a good opportunity to form, as these rocks are often created by the silica from the rock flowing down into the pockets within the lava rocks.
This same process is also responsible for all the jasper found in Washington.
Such jasper tends to be browner or reddish in color betraying the rich iron of the region itself, however green varieties are also fairly common as well.
Rockhounding in Washington has also over time revealed Sulfur and Iron rich pyrite and Calcium based calcite near Shelton, and Magnesium rich Talc near Wenatchee.
This variety shows the complexity of rockhounding in Washington, the reason for the popularity of the hobby in this state and of course the importance which rock hounding holds in better understanding the states rich heritage and wilderness.
Much of the richness of Washington's agates is a result of a long and often violent geological history filled with volcanic eruptions and huge sediment carrying glaciers.
The state of Washington can be has many geological regions and sub-regions thanks to the various flows, external rocks, and glaciers which have made their home throughout the state over the last 100 million years.
The western part of the state has been dominated by arc volcanism, in which the oceanic plate is submerged along with water rich rocks under the continental plate.
The water and more volatile rocks from the oceanic plate lower the melting point of the mantle, allowing the mantle to rise up and break through the continental crusts.
It is these actions which would seem to help make Washington State one of the best places to find agates in the country and which allows it to have such a rich verity of agates including the famous Ellensburg Blue Agate.
In some cases islands from distant regions are carried on the moving contents and will get scraped off and deposited in western Washington as the oceanic plate carrying them gets submerged.
This has create a number of rock locations called exotic terranes, rocks which are historically and geologically separate from the region in which they are found.
Moving East one finds what once the path of the Yellowstone hotspot, which created reddish-brown mineral deposits.
Such deposits are common in areas of lava flows rich in iron.
As lava rocks and ash are typically rich in silica's, and the viscous nature of these flows allows for many pockets within the rock, agates have a good opportunity to form, as these rocks are often created by the silica from the rock flowing down into the pockets within the lava rocks.
This same process is also responsible for all the jasper found in Washington.
Such jasper tends to be browner or reddish in color betraying the rich iron of the region itself, however green varieties are also fairly common as well.
Rockhounding in Washington has also over time revealed Sulfur and Iron rich pyrite and Calcium based calcite near Shelton, and Magnesium rich Talc near Wenatchee.
This variety shows the complexity of rockhounding in Washington, the reason for the popularity of the hobby in this state and of course the importance which rock hounding holds in better understanding the states rich heritage and wilderness.
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